High-pressure pumps are commonly used to pump abrasive slurries such as tile-glazing clays, flue gas desulferization, and coating slurries for investment castings. Pump life is a significant factor that must be considered when designing pumps suitable for pumping abrasive slurries. Rotary operated oil backed diaphragm pumps, such as those described in U.S. Pat. Nos. 3,775,030 and 3,884,598, are inherently suited for use as high-pressure pumps capable of pumping abrasive slurries because they require no sliding pistons or rubber seals that are likely to abrade. The durability limitation of such pumps is generally controlled by the inlet and outlet plate and/or ball valves used. Typically, such inlet and outlet plates and/or ball valves fail magnitudes of time sooner than the other pump elements. What is needed is a pump valving assembly having improved abrasion resistance characteristics.